The present application claims priority under 35 U.S.C. xc2xa7 119 of German Patent Application No. 100 16 492.7, filed on Apr. 1, 2000, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a device and an associated process for removing a fibrous material web, e.g., a cardboard, paper, or tissue web, from a drying section of a machine for producing and/or refining the fibrous material web so that the material web is guided into a catch device or trap. In the machine, the fibrous material web runs over heated drying cylinders and guidance rolls in the drying section and is guided at least predominately by at least one drying wire.
2. Discussion of Background Information
When a paper machine is started up, the paper web is transferred in sections, i.e., after reaching a subsequent section, the paper web is guided into a catch device or trap in the form of a vat. In this vat, the paper web is redissolved and is readmitted to the production process.
For this purpose, the paper web should be separated from the drying wire in the drying section and travel on the drying cylinder up to a doctor. However, it may occur here that, at the end of the respective transfer section, the paper web does not travel into the vat, but rather continues to travel with the drying wire in an uncontrolled manner. This usually makes any further transfer impossible and can even cause damage to subsequent units.
During normal operation, good adhesion of the fibrous material web to the drying wire is desired for secure guidance of the fibrous material web, e.g., particularly at high speeds. Furthermore, this is further supported by additional devices in the form of suction devices or air guidance devices.
The present invention provides secure guidance of the fibrous material web through the drying section in an operating state and ensures a controlled removal of the fibrous material web at the end of a transfer section during a transfer state.
The present invention includes a device that is provided with at least one controllable separating device, which at least reduces the adhesion forces between the fibrous material web and the drying wire.
Here, the separating device or devices are only to be used in the case of a transfer and/or a tear in the fibrous material web. In this way, good and secure guidance of the fibrous material web on the drying wire during normal operation is not impaired.
Experiments have shown that at least one separating device should be used for transferring the fibrous material web in the region of the drying section in which the fibrous material web has a dry content of less than about 43%. In this region, the moist fibrous material web tends to adhere more strongly to the drying wire than to the smooth drying cylinder. Therefore, it is advantageous for at least one separating device to be used after the transfer region between a preceding pressing section for dewatering the fibrous material web and the drying section. The direct transfer of the fibrous material web from the last pressing nip of the pressing section into the first drying group of the drying section makes the transfer process not only simpler, but also faster overall because, up to now, the fibrous material web was always removed between the pressing section and the drying section.
Accordingly, at least one drying cylinder in the initial region of the drying section, preferably of the first drying group of the drying section, is provided with at least one separating device. Because of the stretching of the moist fibrous material web, the first drying group should be as short as possible, i.e., the first drying group should have a maximum of three, preferably two, and in particular only one, drying cylinder(s).
With respect to the arrangement of the separating device, there are various possibilities, with it being advantageous, however, to arrange several separating device in the region of one or more drying cylinders. The separating device can be arranged in the wrapping region of a drying cylinder and/or shortly before it and/or after the wrapping region of a drying cylinder. Here, the separating devices, if they are on the side of the drying wire opposite the fibrous material web, can be embodied as air nozzles that direct pressurized air through the drying wire onto the fibrous material web, or as an air guidance element, preferably in the form of a flexible blade running crosswise to the fibrous material web, which partially dams the air border layer carried along by the drying wire and presses it towards the fibrous material web through the drying wire. As a result, in the transfer state, the fibrous material web should continue to travel over the drying cylinder after the removal of the drying wire and should be removed and guided into the intercepting device by a doctor placed against the drying cylinder.
Here, the one or more separation devices can also be part of an air guidance device, which is arranged in the region between the drying cylinder and the guidance roll and which guarantees the secure guidance of the fibrous material web on the drying wire under normal operating conditions.
If the separation devices are arranged on the side of the drying wire opposite the fibrous material web, preferably in the region of a guidance roll, a further possibility results from the fact that the separating device is embodied as a pressure nozzle that directs a pressurized stream of liquid or gas towards the drying wire for the purpose of separating the fibrous material web and, thus, guides the fibrous material web towards the intercepting device.
The present invention is directed to a device for removing a fibrous material web from a drying section of a machine for producing and/or refining the fibrous material web and into a catch device. The drying section includes heated drying cylinders, guidance rolls, and at least one drying wire arranged such that the fibrous material web is guided through the drying section over the heated drying cylinders and the guidance rolls at least predominately by the at least one drying wire. The device includes at least one controllable separating device arranged to at least reduce an adhesion force between the fibrous material web and the at least one drying wire.
In accordance with a feature of the instant invention, the fibrous material web can include one of a cardboard, paper, and tissue web.
According to another feature of the invention, the at least one separating device may be arranged at least one of in a wrapping region of a drying cylinder and shortly before it.
Further, the at least one separating device may be arranged after a wrapping region of a drying cylinder. The at least one separating device can be positioned on a side of the at least one drying wire arranged to carry the fibrous material web. The at least one separating device may be arranged in a region of a guidance roll. Still further, the at least one separating device may include a pressure nozzle arranged to direct a stream of pressurized gas or liquid toward the at least one drying wire, such that the fibrous material web is separated from the at least one drying wire.
According to still another feature of the present invention, the separating device can be arranged on a side of the at least one drying wire opposite the fibrous material web.
The separating device may be embodied as an air nozzle arranged to direct pressurized air through the at least one drying wire toward the fibrous material web.
Moreover, the separating device may be embodied as an air guidance element arranged to at least partially interfere with an air border layer carried along by the at least one drying wire and to press the interfered with part of the air border layer through the at least one drying wire toward the fibrous material web. The air guidance element can include a flexible blade running crosswise to the fibrous material web.
A doctor may be arranged to grip onto the drying cylinder after the wrapping region of the fibrous material web, such that the fibrous material web can be removed.
An air guidance device may include the at least one separation device, which is located in a region between the drying cylinder and the guidance roll and is arranged to provide a secure guidance of the fibrous material web on the at least one drying wire under normal operating conditions.
According to a further feature of the invention, the at least one separating device can include a plurality of separating devices arranged in a region of the drying cylinder.
The drying section may include an initial region including at least one heated drying cylinder. The at least one separating device can be associated with the at least one drying cylinder of the initial region. Further, the initial region can include a maximum of three drying cylinders, at least two drying cylinders, and preferably, only one drying cylinder.
The present invention is directed to a process for removing a fibrous material web from a drying section of a machine for producing and/or refining the fibrous web and into a catch device. The drying section includes heated drying cylinders, guidance rolls, at least one drying wire, and at least one separating device. The process includes guiding the fibrous material web through the drying section over the heated drying cylinders and the guidance rolls at least predominately by the at least one drying wire, and, in an event of at least one of a transfer and a tear in the fibrous material web, actuating the at least one separating device.
According to a feature of the instant invention, the at least one separating device can be used for transferring the fibrous material web in a region of the drying section in which the fibrous material web has a dry content of less than about 43%.
The at least one separating device may be arranged after a transfer region between a previous pressing section for dewatering the fibrous material web and the drying section.
The separating device can include an air nozzle arranged on a side of the at least one drying wire opposite the fibrous material web, and the process may further include directing pressurized air from the air nozzle through the at least one drying wire toward the fibrous material web.
Moreover, the separating device may include an air guidance element, and the process can include at least partially interfering with an air border layer carried along by the at least one drying wire and pressing the interfered with part of the air border layer through the at least one drying wire toward the fibrous material web. The air guidance element may include a flexible blade extending crosswise to the fibrous material web.
The drying section can further include a doctor positioned against a surface of the drying cylinder after the wrapping region of the fibrous material web, and the process can further include removing the fibrous material web from the surface of the drying cylinder with the doctor.
The drying section can include an air guidance device which includes the at least one separation device, the air guidance device being located in a region between the drying cylinder and the guidance roll, and the process may also include securely guiding, via the air guidance device, the fibrous material web on the at least one drying wire under normal operating conditions.
The at least one separating device may include a pressure nozzle positioned on a side of the at least one drying wire arranged to carry the fibrous material web and in a region of a guidance roll, and the process may include directing a stream of pressurized gas or liquid from the pressure nozzle toward the fibrous material web carrying side of the at least one drying wire to separate the fibrous material web from the at least one drying wire.
The present invention is directed to an apparatus for producing and/or refining a fibrous material web including a catch device arranged to receive a portion of the web, whereby the portion of the web is readmitted to a production process, a drying section including a least one drying group, where the at least one drying group includes at least one heated drying cylinder, guidance rolls, at least one drying wire arranged to at least predominantly guide the fibrous material web through the drying section, and at least one controllable separating device arranged to at least reduce an adhesion force between the fibrous material web and the at least one drying wire.
In accordance with a feature of the instant invention, the fibrous material web may include one of a cardboard, paper, and tissue web.
The separating device may include an air deflection element arranged to deflect air entrained by movement of the at least one drying wire through the at least one drying wire, thereby reducing an adhesion force between the at least one drying wire and the fibrous material web.
Moreover, the separating device may include an air jet nozzle arranged to direct air through the at least one drying wire, thereby reducing an adhesion force between the at least one drying wire and the fibrous material web. An air guidance device can be arranged to guide the web between the at least one drying cylinder and an adjacent guidance roll during normal operation, such that the air guidance device includes the at least one separating device. The at least one separating device can be activated and the air guidance device can be deactivated in an event of at least one of a transfer and a tear of the fibrous material web.
According to another feature of the invention, the at least one separating device may include a pressure nozzle arranged to direct a stream of pressurized gas or liquid toward a fibrous material web carrying surface of said at least one drying wire.
In accordance with yet another feature of the present invention, the at least one separating device can be positioned on a side of said at least one drying wire arranged to carry the fibrous material web. The at least one separating device may be arranged in a region of a guidance roll. Further, the at least one separating device can include a pressure nozzle arranged to direct a stream of pressurized gas or liquid toward said at least one drying wire, whereby the fibrous material web is separated from said at least one drying wire.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.